Internal combustion engines having an engine body cooling water passage provided in an engine body and an exhaust pipe cooling water passage provided in an exhaust pipe are known (see JP4911229B2 or CN204476536U, for example). In such internal combustion engines, the engine body and the exhaust pipe are cooled by cooling water flowing through the engine body cooling water passage and the exhaust pipe cooling water passage.
However, conventional internal combustion engines are configured such that cooling water is injected into and discharged from the exhaust pipe cooling water passage separately from the cooling water injected into and discharged from the engine body cooling water passage, and this makes it necessary to provide passages dedicated to the injection and discharge of the cooling water into and from the exhaust pipe cooling water passage, whereby the cooling water passage structure is complicated.